This invention relates to the use of communication elements automatically setting up a data connection in intelligent devices designed for carrying out a data transmission, the data connection set-up being triggered by the approach of two intelligent devices. A concept for automatically setting up a data connection between intelligent devices is known from the specification ECMA/TC32/TG19/2003/12 under the name of “Near Field Communication” (NFC). The purpose of the concept is to make the set-up of a data connection between intelligent devices as simple as possible. The concept provides for two intelligent devices both designed for carrying out an NFC protocol automatically setting up a data connection when they come together at a distance of typically less than 0.2 meters. In a search mode one of the intelligent devices, the initiator, sends a search query which is answered by the second intelligent device, the target. In an immediately following data exchange the two intelligent devices agree on a data transmission mode according to which a data exchange is then effected between the data processing components of the intelligent devices involved.
Detection of whether another intelligent device is located within the response range of the NFC protocol is done in the search mode by cyclically emitting search queries. The parameters provided for the search queries are a transmitting frequency of 13.56 MHz and a magnetic field strength of at least 1.5 A/m up to a maximum of 7.5 A/m. The provided minimum field strength causes a relatively high constant power consumption in intelligent devices ready to carry out an NFC protocol. For devices with limited energy resources, especially for battery-operated devices, this results in a reduction of the possible service life. To reduce this undesirable effect, it can be provided to equip the intelligent devices with a switching device to be actuated by the user for activating the search mode of an NFC unit. However, this possibility at least partly cancels out the goal of particular ease of operation aimed at by the NFC concept, since at least the switching function must be actuated separately.
The standards ISO/IEC 14443 and ISO/IEC 15693 describe a method in which a reading device tries to produce a data connection with another intelligent device (contactless chip card/RFID transponder). For this purpose, the reading device emits a search signal—REQUEST—periodically with high field strength (e.g. 1.5-7.5 A/m according to ISO/IEC 14443) until an intelligent device comes into the response range of the reading device.
German patent application DE 102 06 676 discloses a switching apparatus to be actuated with a transponder, which can be operated almost non-dissipatively as long as no switching process is triggered. The device to be switched has for this purpose a coil which is part of an oscillating circuit which is operated as a substantially unloaded pure oscillating circuit in the detection mode. The resonant frequency tuned in the oscillating circuit is monitored by a frequency observer. When a transponder with a transponder coil is brought close to the detection coil, the resonant frequency of the oscillating circuit changes. This is detected by the frequency observer, which thereupon produces a switching signal which switches on the device to be switched. The proposed solution focuses on the direct change from detection mode to data transmission mode, i.e. on the direct, single-stage switch-on of an intelligent device by means of a coil support which serves primarily as a switching component.